Conan, Kogoro and Ran come across the scene of an accident. A man named Takeshi Yaginuma fell to his death from the staircase of a parking structure. On top of the stairs is Misaki Takizawa, who claims Yaginuma attacked her and accidentally fell. During the investigation, it is discovered Yaginuma is a criminal who broke into Misaki's home and murdered her husband, Akira, and stole 100 million yen worth of precious jewels. Kogoro believes Yaginuma attacked Misaki to silence her, but Conan suspects there's something wrong with Misaki's testimony.

Conan, Ran, and Sonoko are taken to Sera's regular ramen spot, Ramen Ogura, where a murder previously occurred. Inside they find regulars Shono Yuna, Mizushina Sosuke, and Nakanishi Osamu eating. Conan finds the great quantities of condiments and seasoning they put in the food strange. After they leave, employee Sayo reveals a robbery-murder occurred in the neighborhood a few days earlier. The police chased the culprit into the restaurant, and the customers present at the time were Shono, Mizushina and Nakanishi.

The police have narrowed the suspects down to three regulars of the shop: Shono, Mizushina and Nakanishi. After the incident, Yumi ran into her ex-boyfriend Haneda, who says he heard a strange noise every time the culprit took a step. Upon hearing Haneda's story, Conan realizes something. He and Sera solve the mystery behind the reason the culprit was swinging a hose around after committing the crime, determine the reason the culprit continued to visit the shop, and close in on the truth.

After making him drunk, a man was lured to the Kometo Bridge. While his back was temporarily turned, a flashing boomerang quickly drew attention. When the man looked after the mysterious glowing object flying by, he was grabbed his legs and tipped him over the bridge railing to his death in the dried-out riverbed.